docs: def _get_unused_nets(self, vms_to_stop):
          """
          Return a list of nets that used only by the vms in vms_to_stop
          Args:
              vms_to_stop (list of str): The names of the requested vms
          Returns
              list of virt.Network: net objects that used only by
                  vms in vms_to_stop
          Raises:
              utils.LagoUserException: If a vm name doesn't exist
          """
  
          vm_names = [vm.name() for vm in vms_to_stop]
          unused_nets = set()
  
          for vm in vms_to_stop:
              unused_nets = unused_nets.union(vm.nets())
          for vm in self._vms.values():
              if not vm.running() or vm.name() in vm_names:
                  continue
              for net in vm.nets():
                  unused_nets.discard(net)
          nets = [self._nets[net] for net in unused_nets]
  
          return nets